Space Launch System

The Space Launch System, or SLS, is a Space Shuttle-derived heavy launch vehicle being designed by NASA. It follows the cancellation of the Constellation Program, and is to replace the retired Space Shuttle. The NASA Authorization Act of 2010 envisions the transformation of the Ares I and Ares V vehicle designs into a single launch vehicle usable for both crew and cargo. It is to be upgraded over time with more powerful versions.

Design and development

The Space Launch System is a planned a heavy launch vehicle, derived from the Space Shuttle launch system. Its initial capability of the core elements, without an upper stage, will be between 70 metric tons (for the 3-engine, partially fueled core) and 100 metric tons (for the 4-engine, fully fueled core) to low-Earth orbit (LEO) in preparation for missions beyond low-Earth orbit. With the addition of an integrated upper Earth Departure Stage and a fifth SSME-derived core engine, the total lift capability is to be 130 metric tons.^[1][2]

Preliminary information indicated that the current Space Shuttle Main Engines (RS-25D) and Space Shuttle Solid Rocket Boosters would be utilized, and much of the External Tank design would remain the same.^[2] This design would require dramatically less development time than the Ares V heavy lift launch vehicle. On May 24, 2011, NASA announced that development of the Orion from the Constellation program will continue under the name Orion Multi-Purpose Crew Vehicle (MPCV).^[3]

On June 17, 2011, Aerojet announced a strategic partnership with Teledyne Brown to develop and produce a domestic version of the NK-33 engine, with its thrust increased to 2.2 MN (500,000 lbf) at sea level. This booster is to compete against Shuttle-derived solid rocket boosters for the SLS launch vehicle.^[4]

On September 14, 2011, NASA announced its design selection for the new launch system, declaring that it would take the agency's astronauts farther into space than ever before and provide the cornerstone for future U.S. human space exploration efforts^[5][6][7] For early flights SLS has an 8.4-meter diameter core with three RS-25D/E engines, 8.4-meter upper stage with a J-2X engine, and two 5-segment solid rocket boosters.^[8] Later versions will use five RS-25D/E engines and the boosters will be upgraded as well. Selection of the upgraded boosters will be by competitive bid.^[9] The initial two-stage variant will have a similar lift capability to the Saturn INT-20's 60,000 kg. The proposed final variant will have similar lift capacity and height to the original Saturn V.^[10]

By November 2011 NASA had selected five rocket configurations for wind tunnel testing, described in three Low Earth Orbit classes; 70 mt, 95 mt, and 140 mt.^[11]

Program costs

During the joint Senate-NASA presentation in September 2011, it was stated that the SLS program has a projected development cost of $18 billion through 2017, with $10B for the SLS rocket, $6B for the Orion Multi-Purpose Crew Vehicle and $2B for upgrades to the launch pad and other facilities at Kennedy Space Center.^[12] An unofficial NASA document estimates the cost of the program through 2025 will total at least $41B for four 70 metric ton launches (1 unmanned in 2017, 3 manned starting in 2021). The 130 metric ton version should not be ready earlier than 2030.^[13][14]

Criticism

Criticism of SLS falls in several areas including cannibalization of other areas of the space program, "pork barrel" waste, lack of sustainability, lack of new technologies, and lack of development of the commercial space industry. The Space Access Society, Space Frontier Foundation and the Planetary Society called for cancellation arguing that SLS will consume the funds for other projects and will not reduce per pound launch costs.^[15][16][17] The Space Review wrote that the SLS plan will be too costly and will drain resources from NASA's other projects. Rep. Dana Rohrabacher added, "…this plan will suffer the same fate as Constellation: overpromised, under-delivered, and cancelled. Where will we be then?"^[18][19][20]

Others suggest it will cost less to use an existing (Falcon 9, Atlas V, Delta IV), or proposed derivative (Falcon Heavy) American commercial rocket, with on-orbit assembly/fueling depot as needed, rather than develop a new launch vehicle for space exploration without competitive bid for the whole design.^{[21][22][23][24][25][26]} Robert Zubrin suggested that a heavy lift vehicle should be developed for $5 billion on fixed-price request for proposals,^[27] while Elon Musk said he could build one for $2.5 billion.^[28][29]

Critics allege that SLS is a pork barrel spending project.^[30] SpacePolitics.com, Congressman Tom McClinton and other groups argue that the Congressional mandates forcing NASA to use Space Shuttle components for SLS amounts to a de-facto non-competitive, single source requirement assuring contracts to existing shuttle suppliers, and calling the Government Accountability Office (GAO) to investigate possible violations of the Competition in Contracting Act (CICA).^[31][32]

The Competitive Space Task Force, in September 2011, said that the new government launcher directly violates NASA’s charter, the Space Act, and the 1998 Commercial Space Act requirements for NASA to pursue the "fullest possible engagement of commercial providers" and to "seek and encourage, to the maximum extent possible, the fullest commercial use of space".^[33] Space Frontier Foundation co-founder Rick Tumlinson stated that the SLS program harms commercial space development because of "greed, parochialism, and lack of vision of a few congressional pork barrelers".^[34]

Proposed missions and schedule

Current proposed Design Reference Missions include:^[35]

• ISS Back-Up Crew Delivery, a single launch mission of up to four astronauts via a Block 1 SLS/Orion-MPCV without an Interim Cryogenic Propulsion System (iCPS) to the ISS if the Commercial Crew Development program does not come to fruition.
• BEO Uncrewed Lunar Fly-by, or SLS-1, single launch mission of a Block 1 SLS with iCPM and lunar Block 1 Orion-MPCV with a liftoff mass around 66 t. It would be a six to eight day test mission around the moon.
• BEO Crewed Lunar Orbit, or SLS-2, single launch mission of a Block 1 SLS with iCPM and lunar Block 1 Orion-MPCV to LEO with a liftoff mass around 66 t. It would be a twelve to fourteen day crewed mission with four days in lunar orbit.
• GEO vicinity mission, dual launch mission separated by 180 days to Geostationary Orbit. The first a SLS with CPS and cargo hauler. The second a SLS with CPS and Orion-MPCV. Both launches would have a mass of about 110 t.
• a set of lunar missions ranging from EML-1, low lunar orbit, and lunar surface mission. The first two missions would be single launches of SLS with CPM and Orion-MPCV to EML-1 or LLO and would have a mass of 90 t and 95 t respectively. The lunar surface mission set for the late 2020s would be a dual launch separated by 120 days. The first a SLS with CPS and lunar lander. The second a SLS with CPS and Orion-MPCV. Both would enter LLO for lunar orbit rendezvous prior to landing at equatorial or polar sites on the moon. Launches would have masses of about 130 t and 108 t, respectively.

A very preliminary and unofficial schedule based on a worst case budget has outlined some early SLS flights as:^[36]

See also

• Comparison of orbital launch systems
• Jupiter (rocket family)
• DIRECT
• Shuttle-Derived Launch Vehicle

References

External links

• Space Launch System & Multi-Purpose Crew Vehicle page on NASA.gov
• Preliminary Report on Multi-Purpose Crew Vehicle and Space Launch System (PDF). NASA
• Video Animation of the SLS on youtube.com